Heavy Metals in River Jega Northwestern Nigeria: Ecological and Human Health Risk Assessment

River Jega in Kebbi State, Nigeria, provides essential ecosystem services such as water for drinking and domestic use, agriculture, transportation, and fishing. However, these activities contribute to pollution and pose health risks, yet the river’s safety has not been assessed in recent years. This study evaluated water samples from the river for levels of heavy metals including cadmium (Cd), copper (Cu), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn). Cd concentrations exceeded the NSDWQ and WHO limit of 0.003 mg/L in all months except December. Fe surpassed the 0.3 mg/L threshold in all months except February whereas Mn concentrations remained below the safe limit of 0.4 mg/L except in September, October, November, and December. Ni exceeded its limit (0.001 mg/L) in September, October, February, March, and April, while Pb was undetectable from September to December but exceeded safe limits of 0.001 mg/L in other months. Cu, Cr, and Zn remained within safe limits (2.0 mg/L, 0.3 and 3 mg/L, respectively) throughout the year. Average daily ingestion (ADI) and dermal contact (ADC) with the heavy metals were within acceptable ranges. However, their hazard quotient (HQ) indicated potential non-carcinogenic risks from Cr ingestion and dermal exposure to Ni and Pb. Carcinogenic risk (CR) and heavy metal pollution index (HPI) values were below critical thresholds. These results suggest that the water may pose a significant health risk. It is imperative to implement routine monitoring programs and enforce stricter regulations on pollutant discharge.